#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;

int main()
{
	string s1("hello world");
	string s2("C++");
	cout << s1 << endl;
	cout << s2 << endl;

	s1.swap(s2);
	cout << s1 << endl;
	cout << s2 << endl;
	return 0;
}